The present invention relates to spinning of yarn, and more particularly to the spinning of yarn using an electrostatic field to collect and align staple fibers for uniform spinning.
The use of an electrostatic field in a spinning operation is known to the art. In a typical prior art operation, staple fibers are injected into an electrostatic field by conventional drafting apparatus that serves as one of the two electrodes creating the electrostatic field, and a twisting device, which serves as the other cooperating electrode, twists and withdraws the fibers from the field in the form of spun yarn. The electrostatic field causes the fibers to receive a net charge as they enter the field and to receive an additional polarization charge which is superposed on the net charge after leaving the feed apparatus. The net charge causes the fibers to be attracted toward the twisting device and the superposed polarization charge causes the fibers to be straightened and simultaneously to migrate toward the line of highest electrostatic field intensity. Devices using this method are now being operated in limited quantities. However, several problems have been observed with these known devices. In particular, cotton fly is generated by the drafting unit and collects at positions on the apparatus near the fiber assembly zone, and the collected fly in random amounts enters the assembly zone and attaches to the fibers being spun, thereby causing slubs and yarn breaks. Suction has been tried at the drafting apparatus to remove fly before it enters the electrostatic field, but this has not been wholly effective and results in some usable staple fibers being removed with the fly. Furthermore, external physical and electrical influences disturb the uniform flow of staple fibers to the assembly zone which is not normally enclosed or protected from these influences. The adverse external influences include aerodynamic gusts and distortion of the electrostatic field by foreign objects placed inadvertently near the fiber assembly zone which disturb uniform fiber flow. Also, machine operators can receive electrical shocks by inadvertently touching the unenclosed high voltage electrodes while performing fly cleaning duties during operation. Past attempts at enclosing the fiber assembly zone have been made using insulating dielectric materials. Unfortunately the dielectric materials became charged by the electrostatic field causing waste fly and fibers to accumulate on the dielectric enclosure, which thereby provided a new source for slubs and end breaks. Furthermore, the dielectric materials, although electrically insulating, do not isolate the electrostatic field from external electrical forces which can distort the field.
An example of a prior art spinning operation using an electrostatic field is disclosed in Senturk and Aschenbrenner U.S. Pat. No. 3,845,611, issued Nov. 5, 1974, For Method and Apparatus for Producing Composite Yarn, wherein a core yarn is fed through the electrostatic field to collect the fibers thereon and is subjected to a false twisting to effect twisting of the fibers on the surface of the core. However, neither this prior art example nor any other known prior operation of the general type provides effective isolation of the fibers in the electrostatic field from external physical and electrical disturbances or any effective means of dealing with the problem of fly and waste accumulation and depositing in the spun yarn.
In contrast, the present invention provides shielding or isolation of the electrostatic field from external physical and electrical disturbances and effectively collects and removes fly and other waste material so that high quality uniform spun yarn can be produced continuously in a commercially satisfactory manner.